Wednesday, December 30, 2009

I wanted to take the self centering design with hinges into a different direction today - the goal was to create a model that is very lightweight and fits well in a backpack.

First, I replaced the massive 12 mm stainless steel rods with 12 mm steel tubes. That stuff is a lot lighter, but of course less solid. So I had to give up the "W" form and go back to a classical "Y" design. This necessarily means that the super low fork of the "W" has to be given up some, you simply add 12 mm fork height. Still, a low fork is possible.

Next, I chose much smaller ball bearings, from RC controlled model cars. This allowed me to use a much thinner aluminum tube as a grip.

I kept the hinges because of the band life and also because they make the slingshot easier to be stowed away.

It works! The last "W" model weighs 800 gramms (almost two lbs), this one is just 200 gramms! 75% lighter.

I still prefer my full blown "W", but this self centers just as good and maybe the slightly higher fork has a psychological advantage for those who are afraid to hit their hand.

Monday, December 28, 2009

I noticed that the rotating grip did not self center when a very strong band set was fully drawn out.

The rotating mechanism was just a steel tube that rotated around a thinner steel tube, the thinner tube beeing welded to the frame. It obviously had too much friction to rotate when the system was set under full pressure.

So I ordered some parts and enhanced the setup.

I added two ball bearings, originally from a motorcycle engine. I pressed them on the 12 mm steel rod that was welded to the frame, then pressed everything into a fitting aluminium tube (the grip). I cooled and heated the parts for the pressing. They are totally firm and there is NO play.

It works very well Now the grip rotates smoothly, even when I draw out my toughest bands.

Friday, December 25, 2009

OK, I took the challenge and made an arrow shooting slingshot. I like lead and steel balls, but I realize that an arrow with a broad head can cause more damage. Those who want to hunt larger animals may have more success with arrows. So, here is my idea about how to shoot arrows from a slingshot.

Of course I had watched the "Hunt big game with a slingshot" video series on youtube, and I think the "whisker buscuit" idea is valuable. But I did not want to spend 20 to 50 Euros just on the biscuit!

So I had to solve a number of problems.

1. The draw length limitation

Arrows are rarely longer than 32", and such long arrows weigh more than a .75" (19mm) lead ball! An increase of the draw length beyond 32" is absolutely necessary to achieve serious speed.

So I added two metal tubes to the grip, moving the whisker biuscuit about ten inches towards the shooter. This way, you can draw out a 32" arrow 42" from the pouch.

2. The pouch problem

Gripping the rear end of an arrow though a leather pouch is much harder than gripping a thick lead ball. The "golf tee" solution proved negative for the balance of the arrow, so I had to solve the issue otherwise.

The solution: A change to the pouch! Close to the band attachment, one more hole was punched to either side of the pouch. Through these holes, rubber bands had been tied to both the upper and the lower rim of the pouch.

This allows you to hold the bunched up rubber just like a slingshot ball, and it automatically squeezes the arrow tightly in place. Problem solved.

3. Cheap whisker biscuit

A whisker biscuit is essentially just a brush that is formed like a ring, with the "whiskers" directing to the center of the ring. It guides the arrow, but it lets the stabilizers (feathers, rails, whatever) pass easily. Very nice!

So I decided to go with a whisker biscuit, which I made myself, from one dollar baby bottle brushes. I simply bended the brushes, cut off all excess and tied two of them together so they form a ring. This works, and is really cheap.

Sunday, December 20, 2009

Several people have expressed concern about hitting your hand if the fork is too low.

I now use just 2.5 cm fork height above the hand in my "W" designs. This results to extremely low strain on the wrist, making the slingshot much more controllable.

I tested the setup with lots of super slowmotion stuff (1200 fps recording speed). The ball does not even come close to hit my hand.

But in order to confirm the field tests, I have started to calculate the setup.

It comes down to the research of Sir Isaac Newton.

He came up with so-called gravity laws.

The earth acceleration is 9,81 m/sec*sec.

Let us assume you have a draw length of 1,20 m (that is quite long). And let us further assume that the ball (15mm diameter, .60") flies with 65 m/sec at the end of the acceleration (V0 = 65 m/s, at the fork). That would mean that the average speed is 32,5 m/sec between pouch and fork.

In this case the ball would need 0,037 seconds (37 milliseconds) to reach your hand.

The 15 mm ball passes the fork with its lower rim 1,05 cm over the top of the grip (= your hand).

The shot would have to fly as slow as 40 m/sec (at the end of the acceleration, so V0=40m/s) to make the ball just graze the tip of the grip. That would be a very weak shot.

This calculation does not even assume that the pouch moves towards the fork tips and counterbalances the gravity (a slight upwards vector is applied to the ball). So in reality, the drop is even less substantial.

But of course it would be easy to add another safety margin by making the fork ends higher. It would spoil the effectiveness of the design, though. And then of course the ball may still fall out of your pouch and then hit your foot. Ouch!

So I think it is fair to say that my design is well thought through, supported by the laws of physics and proven by field tests using professional equipment.

Bill Herriman pointed out to me that there is enhanced danger if you do wing shooting (= trying to hit a flying target). That is certainly true, as you may move the slingshot upwards during the shot. This would ruin the safety margin and I do not think that my "W" would be a safe design for wing shooting.

Saturday, December 19, 2009

The self centering "W" slingshot (original idea by Bill Herriman) is my preferred design right now. And many people love it, too, they want to have one... but as you know, I do not sell my slingshots.

So I have been thinking about a "How to" video. Problem is that for the stainless steel "W", you need welding gear and other rather expensive and unusual tools. People don't have these tools at home, so I had to come up with a wooden "W".

It turned out rather well, no metalworks at all. It is more bulky (10% lighter, though), but it shoots just as good. I am very pleased with the stability - no wonder, 1" wooden rods can take some strain.

This means that proof is needed to show that the construction lasts at least five shots. So The Slingshot Channel did another video about some shooting with the "SHTF" slingshot. Not only did it last five shots, it also cracked a coconut!

Friday, December 11, 2009

as an active member of several "survivalists" forums, I am constantly asked for advice about how to make a slingshot with standard supplies. So no fancy Thera Band or Linatex. No power tools. Maybe not even a nice natural fork.

I spent some time thinking about it. The most obvious question is where to find good rubber. Inner tubes and so on are, as we all know, usually not appropriate, and the few types that work are hard to find. Then I found the solution: Condoms. Those are made from natural latex and are of pretty good quality. Of course you need a bunch of them for a good slingshot.

Next, how to make a fork when you have nothing that looks like a fork? Mels page had the answer, the "African" way. Simply cut two 20 cm pieces from a broomstick, carve a wedge from the same wood and fix everything in place with duct tape. It works, and it is very solid and surprisingly comfortable to hold.

The result is a truly ugly, even disgusting slingshot - but one that works really well.

OK, we just hit the 200th follower of this blog. Fantastic! This means that on the 15th, the drawing will result in 15 winners! Each one will win a hand made "Baby Hook" EDC slingshot, complete with bands and ready for action.

Thursday, December 3, 2009

The "V" slingshot still is one of my most popular designs. The one-piece rubber, the pulley based draw entension and the self-centering truly are clear advantages over other designs.

But there are drawbacks. Especially the ergonomics are a problem. I had 50 units made about a year ago, and sold them at cost to fellow enthusiasts. Many of them liked it (and by now own a valuable collector's item), but several people expressed justified critizism regarding the ergonomics.

My big, meaty hands have a natural "padding" so for me it is not hard to hold the V, but I can see how others don't like it as much as I do.

Also, several people reported fork hits, not uncommon when you shoot slingshots with narrow forks. Just a little canting, to subtle for the shooter's eye to see, and bang! A precious pulley is dead, the metal permanently deformed.

I solved the nasty fork hit issue with the rotating handle of the "W", another advanced design that I like very much. The round, smooth and self centering of the "W" makes it my favorite slingshot right now. But of course the "W" has no draw length increase and also no one-piece, self centering rubber.

So the idea is to combine both designs. I have been thinking hard about that and I feel I have a viable idea. Why not attach the rotating steel handle to the "V"?

But of course the "V" has to be out of the way of the shooter's fist. So you have to attach it out front, in order to allow free rotation. Problem is that the fork tips have to be level with the shooter's hand, or else the slingshot would inevitably rotate TOWARDS the shooter.

The solution is to attach the "V" with an angle. This way the laws of physics work!

Can't wait for the weekend to test this idea. Stay tuned for another video.

Tuesday, December 1, 2009

When you read this, you probably wnat to participate in the drawing. That's right, on Dec. 15, 2009, I will select (on a random basis) 10 of my blog subscribers. It does not matter if you have signed up before (just three people had).

I will give away 10 "Baby Hook" slingshots, ready for action with a complete set of bands.

An I will go to 15 slingshots should we see more than 200 subscribers in the 15th!

Thanks, and I promise to entertain you with new slingshots and slingshot news in the future.

BTW: In order to sign up, you must click on "Verfolgen" in the upper right part of the screen.

If you already have a google account, then it is very easy to do that. Sorry for the German GUI, but I could not make the blogspot software coming up in English.